更新字典中的键值

Question

I am trying to write code for the following: The idea is to have a storage/inventory dictionary and then have the key values be reduced by certain household tasks. Eg cleaning, cooking etc.

This would be the storage dictionary:

cupboard= {"cookies":30,
    "coffee":3, 
    "washingpowder": 5,
    "cleaningspray": 5,
    'Pasta': 0.5,
    'Tomato': 4, 
    'Beef': 2, 
    'Potato': 2, 
    'Flour': 0.2, 
    'Milk': 1, 
    "Burger buns": 6}

now this is the code that I wrote to try and reduce one single key's value (idea is that the action "cleaning" reduces the key "cleaning spray" by one cleaning unit = 0.5

cleaning_amount = 0.5
def cleaning(room):
    while cupboard["cleaningspray"] <0.5:
        cleaned = {key: cupboard.get(key) - cleaning_amount for key in cupboard}
        return cupboard
    
livingroom = 1*cleaning_amount

cleaning(livingroom)
        
print(cupboard)

but it returns this, which is the same dictionary as before, with no updated values

{'cookies': 30, 'coffee': 3, 'washingpowder': 5, 'cleaningspray': 5, 'Pasta': 0.5, 'Tomato': 4, 'Beef': 2, 'Potato': 2, 'Flour': 0.2, 'Milk': 1, 'Burger buns': 6}

Can anybody help?

Thank you!!

picture attached to see indents etc.

Answer 1

So I believe the reason that the values don't change is because it is being done in a for loop.

eg

list_values = [1, 2, 3, 4, 5]

new_variable = [num + 1 for num in list_values]

print("list_values", list_values) # The original list_values variable doesn't change
print("new_variable", new_variable) # This new variable holds the required value

This returns:

list_values [1, 2, 3, 4, 5] 
new_variable [2, 3, 4, 5, 6]

So to fix the problem, you can use the 'new_variable'

So, now that the concept is clear (I hope), in your case it would be something like this

def cleaning():
    while cupboard["cleaningspray"] > 0.5: # Also here, i beleive you intend to have `>` 
                                                   #and not `<` in the original code
        cleaned = {key: cupboard.get(key) - cleaning_amount for key in cupboard} 
        return cleaned

We return the 'new_variable' that is cleaned so it can be assigned to the original dictionary variable as follows if required: cupboard = cleaning()

EDIT: Also, as @dk-bo commented, if you intend to only have the operation carry out once... an if statement would also do the job

if cupboard["cleaningspray"] > 0.5: # Again assuming you intended '>' and not '<'

Otherwise, you should keep the return statement outside the while loop

Answer 2

I guess you want to decrease the "cleaningspray" amount depending on the room size (or other factors). I would do it like this:

cleaning_amount = 0.5


def cleaning(cleaning_factor):
    if cupboard["cleaningspray"] > 0.5:
        # reduce the amount of cleaning spray depending on the cleaning_factor and the global cleaning_amount
        cupboard["cleaningspray"] -= cleaning_factor * cleaning_amount


livingroom_cleaning_factor = 1

cleaning(livingroom_cleaning_factor)

print(cupboard)

Output:

{'cookies': 30, 'coffee': 3, 'washingpowder': 5, 'cleaningspray': 4.5, 'Pasta': 0.5, 'Tomato': 4, 'Beef': 2, 'Potato': 2, 'Flour': 0.2, 'Milk': 1, 'Burger buns': 6}